Electroplating bath and process



Patented Oct. 28, 1952 UNITED v STATES PATENT OFFICE ELECTROPLATING BATH AND PROCESS Andrew W. Liger, Wyandotte, Mich assignor to Wyandotte Chemicals Corporation, Wyandotte, Mich a corporation of Michigan I i Drawing. Application Novemberio; 1947; Serial No. 787,255 I Claims. (01. 204- 49) an g plating composition and process".Tha -general object and nature of my invention-is-to provide an electroplating solution which will impart a. bright finish to the metal deposited. My invention isbased on thediscovery that sodium car= boxymethylcellulose" (also called sodium cellulose glycollatez) acts asa'brightening agent in metal plating baths,,particularly inthe electroplating of nickel and cadmium. C

Only a relatively small proportion of the sodium carboxymethylcellulose brightening agent is required to be added to the plating bath. The amount of sodium carboxymethylcellulose additive has been found to be in the range of 005-2. 50% by weight of the electroplating solution.

The following examples serve to illustrate my invention in detail and better to aid those skilled in the art in the understanding of same.-,

EXAMPLE 1 Nickel sulfate (NiSO4.6H2O) 300.0 Nickel chloride NiC12.6HzO) 37.5 Boric acid (H3303) 37.5

pH of bath 3.49 at 275 C.

A solution in the amount of grams of sodium carboxymethylcellulose (medium viscosity grade) and 1 liter of distilled water was then made up by maxing in a Waring Blender. This latter solution was then added to the first prepared electroplating solution, in varying proportions. Specimen brass test plates 1 and inches wide by 3 inches long, and 0.025 inch thickness, were then immersed in the so-prepared solution and electroplated for 11 minutes at a current density of 50 amperes per square foot. The approximate depth of the nickel plate deposited upon the brass specimens was 0.0005 inch. The electroplating solutions were maintained at a temperature of 135:2 F. Two series of electroplating runs were made: one series in a still bath where there was no agitation or stirring, and the other series where the specimen being plated was moved backwards and forwards in a line parallel to the surface of the electrodes at a linear speed of 15 feet per minute. After removal from the plating solution, the plates were then dried and their brightness measured by a reflectometer. The results obtained are tabulated as follows:

1 5; Y:T I j NICKEL-PLATING BATH Percent by Percent Increase Amount (in cc.) of weight of Reflectance in Reflectance: carboxymethylcelsodium g lulose s0lut10n per carboxyp 1 V,

i literlptltating 1 fi3 y1' Still A u A j so u ion ce ose 1 i v present tated tated 0.0 .31 0.001' 29 so 7 s 0. 002 29 35 7 13 0. 005 36 40 33 29 10101 36 162 '33 100 0.02, r 73 H .104 132 "0.05" 71* 71 163 129 From the foregoing results it will be seen that the sodium carboxymethylcellulose addition imparts a marked increase in brightness, on the order of one-third improvement, in both the still and agitated baths, beginning at 0.005% addition to the nickel electroplating solution. At 0.05% addition the increase in brightness reaches a maximum and levels oii.

EXAMPLE 2 A cadmium plating bath solution was made up as follows: I

. G./l. Sodium cyanide (NaCN) 525 Cadmium oxide (CdO) 135 amperes per square foot, producing an electroplate thickness of approximately 0.0005 in. The

temperature of the bath was maintained atv 80:2 F. The brightness of the several cadmium plate specimens, plated in a still bath, was then ascertained as set forth in the following table:

Table II CADMIUM PLATING BATH Percent by weight of sodium car- Reflectance Percent-In boxymethylcellulose present (Still Bath) 'g ggg g From the above results it will be seen that a relatively larger addition of sodium carboxymethylcellulose is required to obtain the brightening effect in the cadmium plating bath as compared to the nickel plating bath. In other words the increase in brightness is first manifest at 0.1% addition of sodium carboxymethylcellulose, reaching a maximum at 0.12% and leveling ofi or slightly decreasing from such maximum thereafter. The sodium carboxymethylcellulose addition may be increased up to 2.5% in the cadmium plating bath while still retaining a brightness increase, as compared to the bath with no such addition.

Other modes of applyingthe principle of my invention may be employed, changes being made as regards to the details described, provided the features stated in any of the following 'claims. or

ODS-0.10% of sodium carboxymethylcellulose, on.

the solution weight basis.

3. An electroplating bath comprising an aqueous solution of sodium cyanide, cadmium oxide,

and containing an addition of 01-05% of sodium carboxymethylcellulose, on the solution weight basis.

4. An electroplating bath comprising an aqueous solution of inorganic metallic compounds selected from the group consisting of an acid solution of a mixture of nickel chloride and nickel sulfate salts, and an alkaline cyanide solution of cadmium oxide; and containing an addition of sodium carboxymethylcellulose ranging, on the solution weight basis, from ODE-010% when the nickel bath is employed and from 01-25% when the cadmium bath is used.

5. The process of brightening deposits of nickel and cadmium in electroplating baths selected from the group consisting of an acid solution of a mixtureof-nickel chloride and nickel sulfate salts and an-alkaline cyanide solution of cadmium oxide, which comprises adding ODE-2.50% by weight of sodium carboxymethylcellulose to the bath.

ANDREW W. LIGER.

REFERENCES CITED The following references are *of record in the file of this patent:

UNITED STATES PATENTS I OTHER REFERENCES Chemical Trade Journal and Chemical Engineering, January 4; 1946, pages 7-8.

Metal Finishing, June 1940. pages 315-17. 

4. AN ELECTROPLATING BATH COMPRISING AN AQUEOUS SOLUTION OF INORGANIC METALLIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF AN ACID SOLUTION OF A MIXTURE OF NICKEL CHLORIDE AND NICKEL SULFATE SALTS, AND AN ALKALINE CYANIDE SOLUTION OF CADMIUM OXIDE; AND CONTAINING AN ADDITION OF SODIUM CARBOXYMETHYLCELLULOSE RANGING, ON THE SOLUTION WEIGHT BASIS, FROM 0.05-0.10% WHEN THE NICKEL BATH IS EMPLOYED AND FROM 0.1-2.5% WHEN THE CADMIUM BATH IS USED. 